Inliners International Forums General Discussion Hi Performance dampner

Can someone tell me the pro`s and con`s of using the small block chevy TCI rattler on my 292?

Even if a SBC balancer in general was a good replacement for the the inline 6 engines, I would find something other than a Rattler to use.
I saw and helped make the very first prototype of one that was made. TCI used our shop as the source to do this back in the late 80's. It looked cool and innovative for the time, but after they went into production, I saw quite a few come through our shop that were built by other builders and racers, and you literally had to destroy them to get them off of the cranks. Because of the rattling action inside of them, they would weld themselves to the crank snout. On one BBC, I saw our teardown guy actually have to take a cutoff wheel and a sawzall and cut it apart to access the hub and cut it off to remove it. For those experiences i've had with them, I would never use one.

I heard some good things about ATI st B-Ville this year.

Some bad things about Fluidamper.

Not the company, one of the teams claimed they lost several crankshafts with them, switching brands supposedly cured it.

The crank snout kept twisting off.

Not sure how a large displacement fat block bent 8 balancer experience relates to an I6, but food for thought.

We also had our rounds with the Fluidampr's breaking the snouts off of a lot of dirt track engines as well. Not fun when its a billet crank either. Fortunately, Crower could put them back on at a price much cheaper than a new crank. I know what the problem was with the Fluidampr, don't know if they ever got it resolved though.

OK, so bad idea. I have been told the fisher isn`t being made anymore so any info on an sfi certed balancer being made now?

ATI makes a good one, but they don't have a specific one for the inline 6, but they can build one for you. BHJ has one also that is specific.

I ran a 8in. v8 damper on a 292 in a pulling tractor without any trouble. We had a crank done in Memphis at Crankshaft Spec. and their test came out to show a 8 in damper was the correct size for a inline 6. Hope this helps. Hud

Tome lowe sells one i personally have one and like it haven't ran it yet but in the next week i will

I have used ATI Super Damper on the straight 8 Buick and the GMC 6 and have had great success. This was at the salt flats and drag racing.

A typical older L6 (4 mains, long stroke) only needs a damper in a few places in its working life.
These "orders" are determined by crankshaft stiffness (which can be calculated, but the math is very bad), generally between 200 and 300 cycles per second, and RPM.
Rating common crankshafts by design for stiffness, highest first:
V6
V8
L4
L6
L8
For a 235, only 2 orders (the 3rd and 6th) fall within the normal RPM range. The 9th (and higher) order is too slow for practical use, and the lower orders are above any RPM you would use.
If the engine never sees continuous service very close to these 2 orders it doesn't need a damper. Chrysler tried this (and got it wrong) on the 241 hemi motor: no damper at all, but the motor was used in this range and the cranks broke.
If it does need a damper (viz., 1 of the orders occurs at a common cruising RPM) only the correct damper (tuned to this point) will help.
A billet, carbon-fiber, titanium V8 damper has no effect at these points, it's just money hanging there. It "protects" against harmonics in V8 orders that have no effect in an L6.

Please note: the SEMA damper standard (S.F.I. 18-1) does not rate a damper's effectiveness, or certify that it works at all (let alone on a specific motor) - only that it didn't explode during the test.

Correct, many people confuse the fact that something didn't blowup, so it must be ok....so far!

I am surprised that this thread is active given that this was extant for so long:

https://www.inliners.org/ubbthreads/ubbth...61c4ab9a5e7b329

Additionally, a look at the BHJ website gives you an insight into what's involved in a harmonic damper.

Thank all of you for your input. Communicating with people who know what they are talking about keeps me from making my usual stupid mistakes. Dan

Dan, I had used an ATI harmonic damper, but it would weld it self to the crank, I then went to a fluidampr and my problems went away.

I talked to ATI and they would not give me any help, I thought the rubbers were wrong, and I was right,in talking to Glen Self he said that you need number 88 rubbers for an inline.

Also I am one of the few that use a forged crank, it flexes more but won't break.

The old catalogs from ATI used to show the ATI vs the Rattler vs the Fluidampr it showed the Fluidampr was the best to 6000 RPM then the ATI was better, the Rattler was the worst.
ATI no longer shows this chart in their catalog.

Hope this helps

it would weld it self to the crank

Typically, this means it was slightly undersize (not tight enough) and would fret slightly during periods of excitation.
That would be fatal to any snout device.

Damper was slightly oversize?, not tight enough?

Or crank snout is slightly undersize?

The Rattlers we had experience with had .0015"-.002" interference fit, which is what all other aftermarket balancers have including the OEM ones, so they were not too loose on the snout. It was an inherent flaw with the "rattling" of it as it was in operation that was causing the galling of that brand. They gave us two dozen of the first batch they made, but we never used them, Headrick finally threw them all in the dumpster after we had them for a couple of years and saw all the problems others were having with them. Even though we helped TCI in the prototyping of them, Headrick didn't think the design was going to dampen much, they still are basically a solid balancer with metal slugs loose inside of it, kinda' like the balls they put into tires that you can't balance with normal techniques. That concept might work for tires, but it doesn't for cranks!

Talked with mr. pierce up in Wash and sent him some money. nice guy.

sparks, is that an SFI or don't you need one?

The fit was exactly .ooo1 just what they call for.
It's was just the wrong frequency for my setup, have not had any problems with the Fluidampr

Maybe the frequency of a steel forged crank is different than a junk cast one.

GM first made the forged crank then a cast one of the same design, to lower the cost, but it did not work so they made it fully counter weighted to try and make the cheaper one work.

Back in the day Headrick said he would only get 12-14 runs on a cast crank.

That's why I have used a steel one since 1964 when we started to run this engine.

Since I run a turbo I don't need to turn much over 6000 RPM.

Now making over 900 HP.

turbo,the car this motor is going in is a bracket altered to allow me and my grand kids to go play without breaking the bank. I have already done the hi-buck stuff and can`t afford it (retired) anymore. I`m talking about an 11 second car. Your car sounds very immpressive, would love to see it run.

We actually changed the cranks out every 20 passes because that's the most runs we ever got out of one before they broke. So Jim decided that at twenty passes, we would change cranks regardless.
It didn't matter if they were steel or not, Jim used them at first, but they still never lasted as long as the cast cranks. The steel cranks were always more expensive to buy, so Jim didn't see the need to spend extra money for a crank that wasn't going to last any longer than a cast one.
The reason they only lasted for only twenty passes was that Cotton would leave the starting line at between 10,500 and 11,200 RPM, that coupled with dropping the clutch in a 3240 lb car was very abusive to the cranks and other parts. Once they switched to Comp Eliminator and the rear engine dragster, the launch RPM was at a more sane 5500 to 6000 RPM, and the cast cranks lasted indefinately then.

ID of the damper hub should be an interference fit (smaller than the snout OD), so not big enough = not enough press.
That may just be bad planning - they didn't think it would move.
It might also be QC, the hole is/has:
1. taper
2. rough interior finish
3. elliptical

I'm surprised that there are not more warning labels:
"Attention: this product must be press-fit on to your crankshaft nose. Its inside diameter is correctly sized for an interference fit to your original, undamaged crankshaft nose. Never remove material from either one to make assembly easier.
Boiling water on the hub opening and ice or freon on the nose just prior to mating may help. Do not use a torch on the damper without Tempilstick etc. or the rubber/fluid will be ruined.
If the crankshaft is still in the block, the rear flange or hub must be backstopped with a heavy and incompressible object to prevent damper insertion pressure from destroying the crankshaft's thrust bearing."

The Fluidampr comes with explicit directions on the size.

You don't want to heat, cool or do anything to the crank just a little anti-seize. You need to use an installer to pull it on the crank no problem with the thrust if you do this.

Never broke a crank from use, my car is 3300 lbs 900+HP comes off on transbrake at 5500 RPM.

HP isn't what breaks the cranks, its operating them in an RPM range where the harmonics affect the crank. Your safe at 5500 RPM even if you made twice the HP you are now, because your well below the harmonic danger zone.

Yes this is true to a point, cranks actually go through many harmonic zones depending on the RPM.

It's actually torque that tries to break a crank.

So you can apply 900 ft lbs at 5000 and it's safer than like 300 ft lbs at 10,000 RPM.

Ok, we get it.
Now lets see some pics of the progress on that 12 port install.

MBHD

Just for fun, a sample (may not exist) crankshaft and its harmonic orders. Natural frequency: 250 Hz. The orders are located at: RPM = Hz × 60 ÷ N, where N is the order number.
Ranked by severity (magnitude of damage from sustained use), worst on top:
#3 5,000 RPM
#2-1/2 (yes, it's there) 6,000 RPM
#2 7,500 RPM
#6 2,500 RPM
#9 1,667 RPM (pretty weak)
#12 1,250 RPM (almost harmless)
#1 15,000 RPM (pretty strong, but out of reach)

#4, 5, 7, 8, 10, 11 = harmless in an L6

A V8, L4 etc. will have the same orders (if the Hz matches) but which ones are important will be pretty different.

Don't know how to post pictures, will try to get my son to post some, he did all the new fabrication.

Is that a specific order (damaging frequency harmonic orders) for any straight 6, or just your hypothetical?

I can do the math easily enough (the formula you posted is simple enough) but I was curious for the 4200 (OT engine for this thread maybe, but still harmonics).

the story seems to be they have a really bad harmonic somewhere between 6700 and 7300 (some say 7200).

It's a bit more difficult to find since I don't know which order, or the crank's natural frequency.

Hence my question, is that "safe" to call it 3rd order?

That's for all common L6 engines with the usual firing orders (not 2-stroke or flat crank). The 2, 2-1/2 and 3 are very strong and also fall into the RPM range you might need.
The 4200 is probably stiffer than most 4 main engines, some L6 engines have as natural frequencies as high as 300 Hz.
To compare similar crankshafts, factors that weaken them (reduce stiffness) and lower the frequency are:
1. small main journals
2. low number of main journals
3. small rod journals
4. small journal overlap
5. long stroke
6. long overall length
7. long distance between main journals
8. low counterweight mass

If there's really a bad spot at 7,200 it may be a harmonic order, but 240 Hz makes it the 2nd order. The 3rd order will make the frequency, IMHO, too high for the engine design at 360 Hz. The 2-1/2 order is 300 Hz, quite possible.

I don't know that the harmonic occurs right at 7200, I meant to say that the range it supposedly occurs in may end there.

I figure the range starts somewhere just above 6700 as that is where the factory rev limiter seemed to kick in.

Poor phrasing on my part.

Thank you for the information, that makes some sense.